This kind of goes along the same lines as #686214: Add entity information to {url_alias} that it would be nice if we could save extra data about URL aliases within the {url_alias} table itself as a serialized array in {url_alias}.data. For instance, when using Pathauto if someone saves an alias manually we add $path['data']['pathauto'] = FALSE. This way, when someone loads the node that has that alias, edits the title and re-saves it, we know in Pathauto module that we should not try to re-alias the node.